use crate::export::Export;
use wasmer_types::entity::{BoxedSlice, EntityRef, PrimaryMap};
use wasmer_types::{ExternType, FunctionIndex, ImportIndex, MemoryIndex, TableIndex};

/// Import resolver connects imports with available exported values.
pub trait Resolver: Sized {
    /// Resolves an import a WebAssembly module to an export it's hooked up to.
    ///
    /// The `index` provided is the index of the import in the wasm module
    /// that's being resolved. For example 1 means that it's the second import
    /// listed in the wasm module.
    ///
    /// The `module` and `field` arguments provided are the module/field names
    /// listed on the import itself.
    ///
    /// # Notes:
    ///
    /// The index is useful because some WebAssembly modules may rely on that
    /// for resolving ambiguity in their imports. Such as:
    /// ```ignore
    /// (module
    ///   (import "" "" (func))
    ///   (import "" "" (func (param i32) (result i32)))
    /// )
    /// ```
    fn resolve(&self, _index: u32, module: &str, field: &str) -> Option<Export>;
}

/// Import resolver connects imports with available exported values.
///
/// This is a specific subtrait for [`Resolver`] for those users who don't
/// care about the `index`, but only about the `module` and `field` for
/// the resolution.
pub trait NamedResolver {
    /// Resolves an import a WebAssembly module to an export it's hooked up to.
    ///
    /// It receives the `module` and `field` names and return the [`Export`] in
    /// case it's found.
    fn resolve_by_name(&self, module: &str, field: &str) -> Option<Export>;
}

// All NamedResolvers should extend `Resolver`.
impl<T: NamedResolver> Resolver for T {
    /// By default this method will be calling [`NamedResolver::resolve_by_name`],
    /// dismissing the provided `index`.
    fn resolve(&self, _index: u32, module: &str, field: &str) -> Option<Export> {
        self.resolve_by_name(module, field)
    }
}

impl<T: NamedResolver> NamedResolver for &T {
    fn resolve_by_name(&self, module: &str, field: &str) -> Option<Export> {
        (**self).resolve_by_name(module, field)
    }
}

impl NamedResolver for Box<dyn NamedResolver> {
    fn resolve_by_name(&self, module: &str, field: &str) -> Option<Export> {
        (**self).resolve_by_name(module, field)
    }
}

impl NamedResolver for () {
    /// Always returns `None`.
    fn resolve_by_name(&self, _module: &str, _field: &str) -> Option<Export> {
        None
    }
}

/// `Resolver` implementation that always resolves to `None`. Equivalent to `()`.
pub struct NullResolver {}

impl Resolver for NullResolver {
    fn resolve(&self, _idx: u32, _module: &str, _field: &str) -> Option<Export> {
        None
    }
}